The use of sewage mud in agriculture has generated several discussions due to the risks of soil contamination mainly by metals. Due to the intimate contact of the diplopods with soil, they have been successfully used in ecotoxicological analyses. The impact of the external environment in the physiological changes in organs and tissues of different organisms can be reflected by the ultrastructural changes of their cells. Using the transmission electron microscopy, this study aimed to analyze the ultrastructural alterations in the midgut of the diplopod Rhinocricus padbergi exposed to substrate containing sewage mud from a Sewage Treatment Station of São Paulo State, Brazil. Therefore, it was sought to identify cellular alterations resulting from the subchronic exposure (90 days of exposure) of the animals to complex and potentially toxic mixtures such as sewage mud at different concentrations (1%, 10%, and 50%). The control group presented integrity in the cells and tissues that constitute the midgut. The animals exposed to sewage mud at 10% and 50% died before the 90 days of exposure. The analysis of the midgut of the animals exposed to 1% of sewage mud showed alterations in the epithelial cells, cells of the fat body layer, and hepatic cells. The main alterations observed were cytoplasmatic vacuolization, loss of the plasmatic membrane, and nuclear envelope integrity. We conclude that the mud sample presents a mixture of complex substances of cytotoxic and genotoxic action to the diplopod, causing cell death, since both the nucleus and other cellular compartments were damaged.
The aim of this study was to use the diplopod Rhinocricus padbergi as test organism to verify the possible toxic effects of the herbicide trifluralin in a representative of the edaphic fauna. Histological and histochemical techniques were applied in the midgut of the animals after exposure to different concentrations of trifluralin for 7 and 90 days (acute and subchronic exposure, respectively). The individuals from the control group did not present alterations to any of the exposures. In the acute exposure, the group exposed to a quarter and half of the field dose presented an accumulation of cytoplasmic granules in the hepatic cells; the field dose group presented an increase in the rate of epithelial renewal and the group exposed to double the field concentration presented an increase in the release of secretory vesicles. The subchronic response was obtained with the field dose and double field dose because the animals from a quarter and half groups did not survive until the end of the experiment. In both groups, the animals presented disruption of the epithelium and higher occurrence of hemocytes among the hepatic cells. The group exposed to double the field dose presented sites of cytoplasmic vacuolization, dilatation of the intercellular space, increase in the epithelial renewal, and release of secretory vesicles. The results alert for a careful use of this herbicide, since it promoted alterations in the midgut cells of the test organism used.
This study presents the morphological description and histochemical characterization of gill filaments of the Brazilian endemic bivalve Diplodon expansus, aiming to broaden the morphological knowledge of this species and establish the structure of the gills that will serve as control in histopathological studies applied to biomonitoring. The gill filaments are divided into three zones: frontal, intermediate, and abfrontal. In the center of the filament, haemocytes circulate through the haemolymph vessel, which is internally lined by endothelium. The frontal surface of the filament is covered with cilia, the lateral surface exhibits aquifer ducts, and the abfrontal surface presents ciliated and nonciliated cells. The epithelium of the filaments is composed of ciliated cells, nonciliated absorptive cells, and mucocytes. The support of the filaments is made by two specialized structures called skeletal rod and skeletal loop. Based on the obtained information, the gill filaments of the studied species present some peculiar characteristics that are not yet reported in detail in the literature such as the simultaneous presence of skeletal rod and skeletal loop. On the other hand, the general constitution of the filament is similar to that described for both marine and limnic bivalves and seems to be suitable for ecotoxicological studies.
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